Conventionally, surveillance cameras, in-vehicle cameras and the like employ an image processing device for capturing a wide-range image by using a wide-angle lens such as a fisheye lens, correcting image distortion due to the optical distortion of the lens by means of image processing, and outputting the corrected image.
Such an image processing device corrects the image distortion by determining a position in the image before the correction corresponding to a position of a pixel in the corrected image by means of coordinate transformation and interpolating a pixel value at the determined position by using vicinal pixel values. In such processing, a line buffer or the like accessible at high speed is used to make it possible to refer to the vicinal pixel values without processing delay.
When the image distortion is corrected by means of the aforementioned coordinate transformation, the amount of correction is relatively great in the peripheral part of the image as compared to the center of the image. Accordingly, in the corrected image, resolution performance decreases as it goes from the center towards the peripheral part.
In this connection, there has been proposed a technology of compensating for decrease in a sense of resolution caused by the image distortion correction by using edge enhancement processing and setting an enhancement coefficient so that an edge enhancement level increases with increase in the optical image distortion (see Patent Reference 1).